1. Field of the Invention
The present invention relates to an exhaust pipe structure for a motorcycle, and particularly to the structure and arrangement of exhaust pipes extending from each cylinder of an engine.
2. Description of Background Art
In a general exhaust pipe structure of a motorcycle, exhaust pipes extend from each cylinder of an engine. A muffler is connected to the downstream ends of the exhaust pipes on each side, whereby exhaust gas disposed within the muffler is discharged from a tail pipe mounted on the rear end of the muffler.
The temperature of exhaust gas directly after being discharged from the engine is very high. The exhaust pipes exposed to the exhaust gas are likely to be discolored, leading to corrosion from the discolored portion. A technique for solving this problem has been known, for example, as disclosed in Japanese Utility Model Laid-open No. SHO 63-87214, wherein each exhaust pipe has a double-pipe structure for suppressing an increase in the temperature of an outer pipe.
In a prior art motorcycle, a cover is provided near the collected portion of exhaust pipes on each side, and the exhaust pipes are disposed to pass inside the cover.
The above-described exhaust pipe having the double-pipe structure is increased in its pipe diameter as compared with an exhaust pipe having a single-pipe structure. To arrange a plurality of the exhaust pipes, each having a large diameter, inside the cover, the size of the cover must be enlarged. Thereby, the cover cannot be contained in a specified space.
On the other hand, the exhaust pipe having a single-pipe structure solves the problem in terms of space. However, there occurs a disadvantage in that the exhaust pipes are discolored by heat and the cover is also discolored by the heat of the exhaust pipes.